Along with the continuous society development, people have an increasing demand on the quality of food in daily life, vegetables, fruits and meat, etc should be kept in good shape but also in good color with good smell and taste. Currently, refrigerators and refrigerating cabinets are mainly used to keep food fresh, but it is not a good way, since vegetables and fruits of the leaf class will lose their original flavor and nutrition and also get crinkles and spoiled spots when they are kept cold at around zero degree. All refrigerators and refrigerating cabinets in current market as well as the lately released zero-degree fresh-keeping refrigerator have deficiencies in keeping food cold, for example, the food is very likely to get old, faded, deformed, and the fresh keeping can not be ensured in case of long time no power supply, moreover, it is difficult to deal with the oxygen contained inside the refrigerators or refrigerating cabinets which speeds up the process of food oxidation.
Nitrogen is a colourless, innoxious and odourless inert gas, and it has no chemical reactions with food and works effectively to slow down the process of food oxidation so as to keep food fresh. With the above principle that nitrogen keeps food fresh, the invention of a refrigerator and a refrigerating cabinet with fresh-keeping function by supplying nitrogen will bring people new consuming concept by providing better fresh food rich in quality and nutrition. The prior art refrigerator or refrigerating cabinet with fresh-keeping function by supplying nitrogen is only theoretically published, without any disclosure of a practical technical scheme necessary for product manufacture, neither technical solutions for incorporating a nitrogen generator into a refrigerator or refrigerating cabinet, nor technical solutions for detection and control on nitrogen content, etc.